HEATHER L. DEAN - Primate Testing - 2006

Abstract: DESCRIPTION (provided by applicant): Anatomical and
physiological evidence suggest that posterior cingulate cortex (CGp)
participates in sensorimotor transformations. CGp is strongly connected
with visual and premotor cortical areas, and CGp neurons respond
following saccades. Previous studies suggest that the activity of CGp
neurons is modulated by the position of the eye in the orbit, as well as
by saccade direction and amplitude. The -first goal of this project is
to fully quantify the spatial and temporal properties of CGp neurons by
studying single CGp neurons while monkeys (M. mulatta) perform saccadic
trials with or without a delay intervening between target onset and
movement onset. This intervening delay allows for a temporal separation
of neuronal responses to the target and to the movement. The next goal
is to determine whether CGp encodes spatial information in a coordinate
frame anchored to the fovea, head, or world. Single CGp neurons are
studied while monkeys perform delayed-saccade trials from different
initial fixation positions to targets positioned along an axis passing
through the previously-mapped neuronal response field (RF). If the
movement vector accounts for the variance in firing rate a retinotopic
coordinate framework may be used in CGp. If the final eye position is
most important, CGp could be using framework anchored to the head or
world. Differentiating between these possibilities requires comparing
activity on this task before and after rotating the monkey with respect
to the visual targets. Preliminary data suggest that CGp encodes
information in a coordinate framework centered on the head or world
rather than in one that is retinotopic.

1Department of Neurobiology,
2Center for Cognitive
Neuroscience, and 3Department of
Biological Anthropology and Anatomy, Duke University Medical Center,
Durham, North Carolina 27710; and 4Department
of Biological Sciences and 5Center
for the Neural Basis of Cognition, Carnegie Mellon University,
Pittsburgh, Pennsylvania 15213

Submitted 17 July 2003; accepted in final form 9 June 2004
J Neurophysiol 92: 3056-3068, 2004

Surgical procedures
A head-restraint prosthesis and scleral search coil (*Fuchs and Robinson
1966 ; Judge et al. 1980 ) were implanted in an initial aseptic surgical
procedure performed under isoflurane anesthesia. First, the dorsal
rostrum of the skull was exposed and six 2.5-mm holes were drilled
through the skull with standard orthopedic surgical instruments. These
holes were then tapped for 3.5-mm fine-thread orthopedic cortical bone
screws. Sterile orthopedic bone cement (Biomet; Palacos) was used to
bond a stainless steel head post (Crist Instruments) lowered to just
above the skull surface to 6 titanium screws (Zimmer) inserted into the
tapped holes. The Teflon-insulated scleral search coil (Cooner Wire
AS634) was implanted beneath the conjunctiva, passing just rostral to
the insertions of the extraocular muscles (Judge et al. 1980 ). The wire
exited the conjunctiva temporally, exited the orbit subdermally, was
embedded in the bone cement that formed the restraint prosthesis, and
terminated in a gold and plastic electrical connector (Winchester
Electronics/Litton). After surgery, animals received analgesics for a
minimum of 3 days. Antibiotic prophylaxis was initiated intraoperatively
and continued for 7–10 days. Animals were given a 4- to 6-wk recovery
period after surgery.

A second aseptic surgical procedure was performed once animals could
reliably execute all the behavioral tasks used in the study. A stainless
steel recording chamber (Crist Instruments) was positioned
stereotaxically perpendicular to the horizontal plane over a 15-mm
craniotomy and bonded to 4–6 additional orthopedic bone screws and the
original implant with orthopedic bone cement. The recording chamber was
centered stereotaxically at position 0,0, the intersection of the
midsagittal and interaural planes (cf. Olson et al. 1996 ).
Postoperatively, animals received analgesics for a minimum of 3 days and
antibiotics for 7–10 days. The recording chamber was kept clean with
daily antibiotic washes and sealed with replaceable sterile Cilux caps.
Single-cell recording experiments began after a 1-wk postoperative
period.

Behavioral techniques
Access to water was controlled during training and testing, and animals
were habituated to head restraint and trained to perform oculomotor
tasks for a fruit-juice reward using a custom-built software interface (Ryklin
Software). Visual stimuli consisted of light-emitting diodes (LEDs;
LEDtronics), which could be illuminated to appear red, green, or yellow
to normal human observers. The LEDs were fixed on a tangent screen
placed 144.78 cm (57 in.) from the eyes of the animal, forming a grid of
points, separated by 1°, spanning 49° horizontally and 41° vertically.
These LEDs could be illuminated within 1 ms and extinguished within 7 ms
by the computer system controlling the experiments.

Rats, mice, birds, amphibians and other animals have
been excluded from coverage by the Animal Welfare Act. Therefore research
facility reports do not include these animals. As a result of this
situation, a blank report, or one with few animals listed, does not mean
that a facility has not performed experiments on non-reportable animals. A
blank form does mean that the facility in question has not used covered
animals (primates, dogs, cats, rabbits, guinea pigs, hamsters, pigs,
sheep, goats, etc.). Rats and mice alone are believed to comprise over 90%
of the animals used in experimentation. Therefore the majority of animals
used at research facilities are not even counted.